The consumer electronic devices become thinner and the microelectronic systems become much smaller. The battery is a size-limiting factor to the consumer electronic devices. Hence, the micro batteries are widely used in a variety of fields, such as complementary metal-oxide-semiconductor (CMOS), and micro electro mechanical systems (MEMS), for miniaturization. For example, the micro electro mechanical systems (MEMS) have micro mechanic components, sensors, and actuators as autonomous complete systems and it needs to adapt micro batteries for power supply.
An existing method to fabricate fully solid batteries is to form a power storage device in a form of films and all the components of the micro battery, such as the current collectors, the positive and negative electrodes, and the solid electrolyte, are thin layers formed by a deposition scheme.
Micro batteries are often compared to thin film batteries. Generally, the thin film battery fabricating process does not combine the semiconductor packaging techniques for leveraging silicon technologies made in semiconductor fabricating process over the past decades.
Another concerned issue is that most micro batteries are formed in planar shape. Depending on the used materials, the operating voltage of micro battery is between 1 V and 4 V and the value of the operating voltage is limited for certain applications, for example, sensors or actuators require operating voltages higher than several tens of volts. Besides, there is another limiting factor for application wherein the surface capacity of a fully solid micro battery is in a range of several 10 μAh/cm2 to several hundreds μAh/cm2 and it is too low to use.
Mini batteries sold on the current market and fabricated with a coating techniques have a thickness comprised between 300 μm and 650 μm with a surface capacity of a few mAh/cm2. Although the surface capacity of the mini batteries is much greater than that of a micro battery, the thickness disables them to be integrated on an integrated circuit (IC).
Therefore, there is a need for a micro battery structure and a method making the same to address the above deficiencies/issues.